Rash on 3 year old will not go away

My 3 year old daughter went to the doctor about 2-3 weeks ago because she kept itching herself constantly and they prescribed Nystatin. It worked and the itchiness went away. Well like a couple days after it finally went away, some bumps came back and she started itching again. So they sent in more cream and told me to mix Nystatin, triple antibiotic ointment, and hydrocortisone cream 3 times a day which I did. It went away again.

Well the last couple days it’s back AGAIN. I don’t understand why. We haven’t changed anything she uses. She only wears pull ups at night and nap and they’re the same pull ups we’ve always used. She’s always had sensitive skin even as a baby she has always gotten rashes like crazy but I’ve never seen one this bad keep coming back.

Has this happened to anyone else? Could it be her soap? I’m at a loss. I feel so bad for her that we can’t get rid of this.